The continuous concerns of chiropractors have been:
1. Whether, when and how to adjust patients; PA1 2. How to quantify and objectively document palpatory findings of muscle tension and related soft tissue changes; PA1 3. How to improve results by developing methods where patient care continues outside the office, and corrective changes occur between visits; PA1 4. How to monitor dynamic changes in nervous system function during a course of chiropractic care; PA1 5. How to determine which adjunctive procedures are helpful in a given case; PA1 Development of alternatives to radiography for postural analysis in scoliosis screening and lift therapy; and PA1 7. Development of instrumentation and protocols which can be used to demonstrate soft tissue involvement to third parties, including attorneys and insurance companies.
It is well-known, that the electrical potentials associated with muscular activity may be measured and recorded. This technique is known as electromyography ("EMG"). The use of electromyography in patients suffering from low back pain is commonly accepted in the medical community. The osteopathic profession has used electromyography to verify the presence of palpable lesion of the spine.
Generally, EMG electrodes are placed on the surface of the skin overlying the muscles being evaluated, or needle electrodes are employed which penetrate the tissue being studied. In addition to the active electrodes, a ground reference electrode is also applied to the patient. The signal from these electrodes is very feeble and is typically measured in microvolts. A preamplifier, followed by one or more additional stages of amplification boosts the signal to a usable level. Filters minimize the effects of interference arising from sources other than the muscles being studied. The amplified and filtered signal can be measured and/or displayed on a cathode ray tube. In addition, some machines are equipped with recorders which store the information on paper or magnetic media. Older vacuum tube equipment has largely been replaced by solid state apparatus.
Unfortunately, traditional electromyographic instrumentation has problems which limit its practical application in a chiropractic office, in that the equipment is often bulky and expensive and prone to instability and/or interferences; electrode application is complex and time-consuming; interpretation requires a high level of skill gained through extensive experience; and no protocols exist which are specifically designed for chiropractic practice.
Millions of Americans are incapacitated by chronic low back pain, and it is estimated that 80% of the general population will suffer from low back pain some time during their lives. The annual incidence of low back pain among workers has been reported to be 50 per 1,000. Despite the high incidence of low back pain, some clinicians have described 20-85% of all cases as having no definite discernible physical basis. The same is true with respect to cervical spine soft tissue injuries.
Most orthopedic examination procedures involve a physical maneuver designed to elicit pain or reduplicate symptoms. The inherent flaw in such techniques is subjectivity. The Examiner is dependent upon patient response in determining whether a given test is positive or negative. Neurological examination procedures suffer similar shortcomings. Sensory dermatome exams are dependent upon patient response. Manual muscle tests and deep tendon reflexes are dependent upon Examiner interpretation.
Soft tissue injuries often present ambiguous diagnostic findings. Complaints of pain may be accompanied by apparently normal radiographs. Symptoms are often intermittent. Orthopedic and neurological exam findings may be of questionable value because of Examiner bias and the desire of the patient to "prove" that the injury is "real." Thus, low back and cervical spine soft tissue claims are particularly difficult to evaluate. The independent Examiner needs hard data to substantiate claims of injury or malingering.
Electromyographic changes have been demonstrated in low back pain syndromes arising from a wide variety of etiologies. In some cases, abnormal electromyographic findings were present when other diagnostic tests were negative.
Surface electrode electromyography has been successfully employed by a number of investigators assessing low back pain. It has been demonstrated that muscular pain is associated with increased EMG activity. According to Dolce, et al, Psychol. Bull. 97, 3:502-520, 1985 ". . . the relation between painful and tender muscles and electromyographic activity are equivocal." They further state that "The most prevalent etiological hypothesis for myogenic back pain over the years has been that patients suffer due to increased muscle tension or spasm, although a model emphasizing low or asymmetric muscle activity has also been postulated."
Muscle tension backaches are frequently seen in chiropractic practice. It has been proposed that the muscular hyperactivity associated with back pain is due to a "vicious cycle" of pain producing tension and tension producing pain. This process is thought to be part of a protective mechanism for lesions of the spinal column. It is believed that increased involuntary muscle activity is an etiologic factor in chronic pain. In addition, it has been suggested that splinting and tensing of muscles leads to decreased blood flow, causing ischemic pain. Investigators have also discovered that back pain subjects demonstrate a generalized and sustained increase in skeletal muscle activity. Muscle spasm, therefore, is thought to be the "common denominator" in a variety of myogenic pain syndromes including fibrositis, interstitial myofibrositis, myogelosis, muscular rheumatism, nonarticular rheumatism, myofascial pain syndrome, myofascitis, myalgia, and trigger point pain.
Other investigators have described another mechanism to explain the muscular hyperactivity associated with spinal lesions. Facilitation of the anterior horn cells of the spinal cord has been demonstrated in "lesioned" segments. These cells are associated with efferent motor signals to skeletal muscle. The resulting lower thresholds, and hence increased impulse traffic, cause hypertonicity.
Clinical manifestations of vertebral subluxations often include hypertonicity, hyperalgesia, and decreased mobility. Research by Denslow, et al. JAOA 41:175, 1941 demonstrated that palpable spinal "lesions" correlated well with altered electromyographic activity. Electromyography may, therefore, be useful in quantifying aberrant muscular activity with could formerly be detected solely by palpation.
In addition to backache associated with local myospasm, abnormal electromyographic patterns have been demonstrated in patients with radicular symptoms. Khatri, et al., Arch. Neural., 41:594-497, 1984, used needle electromyography and computer tomography to examine 80 patients with low back pain accompanied by radiation down one or both extremities. The radiculpathies were due to disc involvement, canal stenosis, neural foramen narrowing, or facet joint degeneration. Khatri, et al., concluded: "The CT and EMG often agree. However, an abnormal EMG seems to correlate better with the demonstrated course of radiculopathy than CT."
Metastatic spinal or paraspinal disease may demonstrate abnormal electromyographic patterns. Boruta, et al. reported 54 cases with suspicious electromyograms who had known carcinoma at the time of admission. Boruta, et al. concluded: "Electromyography has been observed as a valuable adjunct in demonstrated paraspinous muscle metastasis in patients presenting with lumbosacral pain who had a known antecedent primary malignancy." In 16 additional cases without an antecedent history of malignancy, abnormal electromyographic findings were noted. In all 16 cases, a previously unsuspected metastatic malignancy was identified.
In addition to these conditions, electromyography has been used to evaluate manifestations of lumbar spinal canal stenosis, lumbar disc herniation, facet involvement, and abomalies of L-5. The effect of surgery, including laminectomy and surgery for nerve root compression have been studied using electromyography. Pfeiffer Acta. Univ. Carolina (Med.) suppl. 21:37-38, 1965, used electromyography to evaluate disturbances in spinal statics and dynamics in workers subjected to overstrain.
In the chiropractic profession, electromyography has been used primarily as a research tool. Electromyography has not been used extensively in the clinical practice of chiropractics. This may be due to a number of factors, including the cost and complexity of the apparatus, the time required to perform the examination, and a general lack of understanding of how electromyographic data may be useful to the chiropractic practioner.
Kent, et al., Digest of Chiro. Econ. 21, 4:30-33, 1979, used electromyography to evaluate a "vertebral challenge" technique of spinal analysis. Surface electrodes were applied to the paravertebral region. A two channel Meditron electromyograph was used, permitting the simultaneous display of potentials on each side of the spinal column.
Triano. JMPT 6, 1:13-16, Mar. 1983, employed electromyography as evidence for use of lift therapy. Thirty nine subjects with low back pain were examined using postural electromyography to assess their responses to heel lifts and ischial supports. He concluded that electromyography provided a greater degree of accuracy in lift placement than traditional radiographic methods.
Meeker. et al., JMPT 9, 4:257-266, Dec. 1986, published a review and summary of current research in neuromusculoskeletal thermography. The technique was compared with electromyography in addition to myelography, computed tomography and clinical and surgical findings. Spector, et al., JMPTs, 2:55-61, June, 1982, described a video integrated measurement system employing a number of non-invasive diagnostic modalities including electromyography, infrared thermography, posturometry, and moire contourography. Emphasis was placed upon the use of this system in biofeedback training.
After using several commercial electromyographic instruments, the inventor became involved in the development of equipment that could be used efficiently and accurately in the chiropractic office. The Hartfield 301 EMG scanner was the result of this effort (Hartfield Instruments Co., Wurtsboro, N.Y.). This instrument eliminates many of the shortcomings of earlier equipment.
This hand-held instrument permits rapid measurement of EMG potentials. The electrodes, preamplifier, readout, and related circuitry are contained in one compact unit. No complex electrode/cable sets need to be applied. The electrodes are "surface" electrodes, i.e., they are simply held against the site to be examiner.
The hand-held unit is equipped with silver-silver chloride post electrodes 2.5 cm apart. A ground reference electrode is placed on the wrist of the patient being examined. The electrodes are directly connected to a high impedance preamplifier. By placing the preamplifier at the electrode site, artifacts associated with environmental sources of electrical signals can be minimized.
A display is built into the hand-held unit, providing a digital readout of electromyographic potentials in microvolts. The instrument provides a bandwidth of 100 Hz to 200 Hz. If desired, signals may be fed from a hand-held electrode/preamplifier unit to a microcomputer to record and analyze the signals.
Biederman, Biofeedback and Self-Regulation, 9, 4:451-485, 1984, questioned the reliability of surface electrode electromyography in evaluating low back pain patients. Alleged sources of error cited were movement of the body, electrode placement, and electronic equipment instability. The equipment and protocols used by Biederman, however, are very different from those employed by the inventors. Cram performed a test-retest reliability study using this instrumentation. It was found that measurements of the trapesius were highly unstable, cephalic muscles showed good stability, and the paraspinal musculature in the lumbar region was highly stable.